1. Technical Field
The present disclosure relates to open or endoscopic surgical instruments and methods for treating tissue. More particularly, the present disclosure relates to a system and method for determining proximity of a surgical device relative to nerve tissue by monitoring nerve responses.
2. Background of Related Art
A hemostat or forceps is a simple plier-like tool that uses mechanical action between its jaws to constrict vessels and is commonly used in open surgical procedures to grasp, dissect and/or clamp tissue. Electrosurgical forceps utilize both mechanical clamping action and electrical energy to effect hemostasis by heating the tissue and blood vessels to coagulate, cauterize and/or seal tissue.
Over the last several decades, more and more surgeons are complementing traditional open methods of gaining access to vital organs and body cavities with endoscopes and endoscopic instruments that access organs through small puncture-like incisions. Endoscopic instruments are inserted into the patient through a cannula, or port, that has been made with a trocar. Typical sizes for cannulas range from three millimeters to twelve millimeters. Smaller cannulas are usually preferred, which, as can be appreciated, ultimately presents a design challenge to instrument manufacturers who must find ways to make surgical instruments that fit through the cannulas.
As mentioned above, by utilizing an electrosurgical instrument, a surgeon can either cauterize, coagulate/desiccate and/or simply reduce or slow bleeding, by controlling the intensity, frequency and duration of the electrosurgical energy applied through the jaw members to the tissue. The electrode of each jaw member is charged to a different electric potential such that when the jaw members grasp tissue, electrical energy can be selectively transferred through the tissue.
Bipolar electrosurgical instruments are known in the art, as are other electrosurgical instruments. Commonly-owned U.S. Patent Application Publication No. 2007-0062017, discloses a bipolar electrosurgical instrument. Conventional bipolar electrosurgical instruments may include a cutting blade, fluid applicator, stapling mechanism or other like feature, in various combinations.
Different types of anatomical structures, i.e. vessels, ducts, organs, may require different energy delivery configurations to effect proper treatment. While a specific energy delivery configuration may be adequate for treating an artery or vein, the same energy delivery configuration may not be suitable for treating a duct. Also, if a surgical device is too close to a non-target nerve structure when energy is supplied to the surgical device, then the nerve structure may be damaged.
During certain procedures, surgeons must identify critical anatomical structures such as large vasculature or urinary or bile ducts. These structures typically need to be avoided or ligated during a procedure, thus requiring a high degree of confidence when identifying such structures.
One complication during laparoscopic procedures in particular, is inadvertently engaging nearby critical anatomical structures due to quick or abrupt movement of instruments within the surgical site, poor visibility, lack of tactile response, confusion of the anatomy from patient to patient, or inadequate control of the instrumentation being utilized to perform the procedure. For example, when performing a thyroidectomy to remove a thyroid gland, the recurrent laryngeal nerve (RLN) needs to be located and preserved. The RLN controls motor function and sensation of larynx (voice box). Identifying and avoiding this structure is important for a successful surgical outcome.
Traditional methods for identifying anatomical structures within the body are based on sensing physical characteristics or physiological attributes of body tissue, and then distinguishing normal from abnormal states from changes in the characteristic or attribute. For example X-ray techniques measure tissue physical density, ultrasound measures acoustic density, and thermal sensing techniques measures differences in tissue heat.
Signature properties of nerve structures such as electrical conductivity, impedance, thermal conductivity, permittivity, and capacitance may be measured and compared to known data to determine proximity of the non-target nerve structure to the surgical device and to distinguish anatomical structures from other anatomical structures and/or known data. If these signature properties can be properly elicited from a nerve structure, measureable values that correspond to these elicited properties may be calculated and compared to known values for purposes of identifying and detecting proximity to the nerve structure.